1. Field of the Invention
The present invention relates to a display apparatus of the type which comprises a passive electro-optical display which has rectangular display area and housing having a lower part in the form of a rectangle that opens upwardly and has a cover which carries the display in a position which is inclined toward the plane of the rectangular lower part, and in which the two longitudinal sides of the rectangular display area lie in parallel planes relative to the plane of the lower housing part and in which the two narrow sides of the rectangular display area are in angle with respect to that plane.
2. Description of the Prior Art
Instruments constructed in the general form noted above are well known in the art, for example one may refer to "Electronics Engineer" 6, (1976), pp. EL1-EL6.
The display contrast in passive displays can be considerably increased when the actual display cell is combined with a so-called fluorescent plate. A fluorescent plate consists of a carrier material which is enriched with fluorescing particles with a refractive index which is greater than one, and which is metallized at its edges and has specific light emergence windows. Such a body collects a great share of the ambient light impinging thereon by means of fluorescent emission and subsequent reflections at its bound surfaces, and the carrier material conveys the captured radiation within itself and emits the same again through its light emergence windows. If an electro-optical display is placed over a fluorescent plate, the display whose display elements are aligned with the light emergence windows, the luminosity of the display is increased by a factor which corresponds to the ratio of the light-collecting to the light-emitting body surface, in a first approximation. More precise details concerning such a display technique is described, and is generally known in the art, in association with the FLAD (fluorescence-activated display), as can be determined, for example, from the article "Light and Economical," published in "Electronics News" on Mar. 25, 1977, or from an article in "Electronics Engineer" 6, (1977) 55.
A FLAD housing must be designed such that the fluorescent plate has a collector surface as large as possible and that the captured light is fed to the individual light emergence windows with the lowest possible losses. Care must therefore by taken that the display still can be satisfactorily recognized in a larger angle range and that the total design has an aesthetic appeal.